1. Field of the Invention
The present invention relates to a novel and industrially advantageous process for producing a 2,6-difluorobenzonitrile (hereinafter referred to as DFBN) useful as raw material of medicines and agricultural chemicals.
2. Description of the Prior Art
Heretofore, a process for producing the DFBN has been known, for example, by the Journal of Agricultural Food Chemistry vol. 21, No. 6, page 933 (1973), Shinjikken kagakukoza vol. 14, No. 1, page 322 (1977), wherein the DFBN is prepared by reacting 2,6-dichlorobenzonitrile (hereinafter referred to as DCBN) with potassium fluoride in the presence of a solvent such as dimethylsulfoxide and sulforane at a temperature higher than 180.degree. C. for at least several hours. However, this process has many disadvantages. For example, (i) the DCBN raw material is hardly available in an economically feasible way, (ii) it is required to use the potassium fluoride considerably in excess of the stoichiometric amount required for said fluorination, for example at a molar ratio of more than twice the stoichiometric amount, and (iii) the yield of the desired DFBN is low. When severe reaction conditions are used to improve te yield, undesirable side reactions and decomposition of the solvent are likely to take place.